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Sebastian Oberst - One of the best experts on this subject based on the ideXlab platform.

  • deep learning for Brake Squeal Brake noise detection characterization and prediction
    Mechanical Systems and Signal Processing, 2021
    Co-Authors: Merten Stender, Sebastian Oberst, Merten Tiedemann, David Spieler, Daniel Schoepflin, Norbert Hoffmann
    Abstract:

    Abstract Despite significant advances in modeling of friction-induced vibrations and Brake Squeal, the majority of industrial research and design is still conducted experimentally, since many aspects of Squeal and its mechanisms involved remain unknown. In practice, measurement data is available in large amounts. We report here for the first time on novel strategies for handling data-intensive vibration testings to gain better insights into friction Brake system vibrations and noise generation mechanisms. Machine learning-based methods to detect and characterize vibrations, to understand sensitivities and to predict Brake Squeal are applied with the aim to illustrate how interdisciplinary approaches can leverage the potential of data science techniques for classical mechanical engineering challenges. In the first part, a deep learning Brake Squeal detector is developed to identify several classes of typical friction noise recordings. The detection method is rooted in recent computer vision techniques for object detection based on convolutional neural networks (CNN). It allows to overcome limitations of classical approaches that solely rely on instantaneous spectral properties of the recorded noise. Results indicate superior detection and characterization quality when compared to a state-of-the-art Brake Squeal detector. In the second part, a recurrent neural network (RNN) is employed to learn the parametric patterns that determine the dynamic stability of an operating Brake system. Given a set of multivariate loading conditions, the RNN learns to predict the noise generation of the structure. The validated RNN represents a virtual twin model for the Squeal behavior of a specific Brake system. It is found that this model can predict the occurrence and the onset of Brake Squeal with high accuracy and that it can identify the complicated patterns and temporal dependencies in the loading conditions that drive the dynamical structure into regimes of instability. Large data sets from commercial Brake system testing are used to train and validate the models. This work is a contribution to the MSSP Special Issue in Honor of Professor Lothar Gaul.

  • Instability prediction of Brake Squeal by nonlinear stability analysis
    2020
    Co-Authors: Zhi Zhang, Sebastian Oberst, Joseph C. S. Lai
    Abstract:

    ABSTRACT Prediction of Brake Squeal as unwanted high frequency noise above 1 kHz remains a challenging problem despite substantial research efforts in the past two decades. Brake Squeal, triggered by friction-induced self-excited vibration, can be caused by many different and interacting mechanisms with nonlinear origins in material properties and boundary conditions. Although Brake Squeal is essentially a nonlinear phenomenon, the standard industrial practice for prediction of Brake Squeal relies on the linear complex eigenvalue analysis which may under-predict or over-predict the number of unstable vibration modes. Brake Squeal can be considered in nonlinear dynamics terms to be caused by a friction-induced self-excitation driven into instability and oscillating in a limit cycle through super-critical Andronov-Hopf bifurcations. In this paper, a nonlinear stability analysis that may be applied to a full Brake system is examined using an unforced 4-DOF friction oscillator with cubic nonlinearity. The local bifurcation behaviour of this model is studied using the normal form theory and the nonlinear stability boundary is evaluated. Differences between results of linear and nonlinear analyses are discussed and the limitations of the linear analysis are highlighted. The energy provided by friction and consumed by damping is calculated by multiple scales method to provide a physical explanation for instability generation

  • impact of an irregular friction formulation on dynamics of a minimal model for Brake Squeal
    Mechanical Systems and Signal Processing, 2018
    Co-Authors: Merten Stender, Sebastian Oberst, Merten Tiedemann, Norbert Hoffmann
    Abstract:

    Abstract Friction-induced vibrations are of major concern in the design of reliable, efficient and comfortable technical systems. Well-known examples for systems susceptible to self-excitation can be found in fluid structure interaction, disk Brake Squeal, rotor dynamics, hip implants noise and many more. While damping elements and amplitude reduction are well-understood in linear systems, nonlinear systems and especially self-excited dynamics still constitute a challenge for damping element design. Additionally, complex dynamical systems exhibit deterministic chaotic cores which add severe sensitivity to initial conditions to the system response. Especially the complex friction interface dynamics remain a challenging task for measurements and modeling. Today, mostly simple and regular friction models are investigated in the field of self-excited Brake system vibrations. This work aims at investigating the effect of high-frequency irregular interface dynamics on the nonlinear dynamical response of a self-excited structure. Special focus is put on the characterization of the system response time series. A low-dimensional minimal model is studied which features self-excitation, gyroscopic effects and friction-induced damping. Additionally, the employed friction formulation exhibits temperature as inner variable and superposed chaotic fluctuations governed by a Lorenz attractor. The time scale of the irregular fluctuations is chosen one order smaller than the overall system dynamics. The influence of those fluctuations on the structural response is studied in various ways, i.e. in time domain and by means of recurrence analysis. The separate time scales are studied in detail and regimes of dynamic interactions are identified. The results of the irregular friction formulation indicate dynamic interactions on multiple time scales, which trigger larger vibration amplitudes as compared to regular friction formulations conventionally studied in the field of friction-induced vibrations.

  • a statistical approach to estimate the lyapunov spectrum in disc Brake Squeal
    Journal of Sound and Vibration, 2015
    Co-Authors: Sebastian Oberst, J C S Lai
    Abstract:

    Abstract The estimation of Squeal propensity of a Brake system from the prediction of unstable vibration modes using the linear complex eigenvalue analysis (CEA) in the frequency domain has its fair share of successes and failures. While the CEA is almost standard practice for the automotive industry, time domain methods and the estimation of Lyapunov spectra have not received much attention in Brake Squeal analyses. One reason is the challenge in estimating the true Lyapunov exponents and their discrimination against spurious ones in experimental data. A novel method based on the application of the Eckmann-Ruelle matrices is proposed here to estimate Lyapunov exponents by using noise in a statistical procedure. It is validated with respect to parameter variations and dimension estimates. By counting the number of non-overlapping confidence intervals for Lyapunov exponent distributions obtained by moving a window of increasing size over bootstrapped same-length estimates of an observation function, a dispersion measure׳s width is calculated and fed into a Bayesian beta-binomial model. Results obtained using this method for benchmark models of white and pink noise as well as the classical Henon map indicate that true Lyapunov exponents can be isolated from spurious ones with high confidence. The method is then applied to accelerometer and microphone data obtained from Brake Squeal tests. Estimated Lyapunov exponents indicate that the pad׳s out-of-plane vibration behaves quasi-periodically on the brink to chaos while the microphone׳s Squeal signal remains periodic.

  • Squeal noise in simple numerical Brake models
    Journal of Sound and Vibration, 2015
    Co-Authors: Sebastian Oberst, Joseph C. S. Lai
    Abstract:

    Abstract Since the early 1920s, automotive disc Brake Squeal has caused warranty issues and customer dissatisfaction. Despite a good deal of progress achieved, predicting Brake Squeal propensity is as difficult as ever as not all mechanisms and interactions are known owing to their highly fugitive complex nature. In recent years, research has been focused on the prediction of unstable vibration modes by the complex eigenvalue analysis (CEA) for the mode-coupling type of instability. There has been very limited consideration given to the calculation of the acoustic radiation properties due to friction contact between a pad and a rotor. Recent analyses using a forced response analysis with harmonic contact pressure excitation indicates negative dissipated energy at some pad eigenfrequencies predicted to be stable by the CEA. A transient nonlinear time domain analysis with no external excitation indicates that Squeal could develop at these eigenfrequencies. Here, the acoustic radiation characteristics of those pad modes are determined by analysing the acoustic power levels and radiation efficiencies of simplified Brake models in the form of a pad rubbing on a plate or on a disc using the acoustic boundary element method based on velocities extracted from the forced response analysis. Results show that unstable pad modes trigger unstable disc vibrations resulting in instantaneous mode Squeal similar to those observed experimentally. Changes in the radiation efficiency with pressure variations are smaller than those with friction coefficient variations and are caused by the phase difference of the velocities out-of-plane vibration between the pad and the disc.

Lai Jcs - One of the best experts on this subject based on the ideXlab platform.

  • Instability analysis of Brake Squeal with uncertain contact conditions
    2018
    Co-Authors: Zhang Z, Oberst S, Lai Jcs
    Abstract:

    © 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling. All rights reserved. Brake Squeal, as a phenomenon of friction-induced self-excited vibrations, has been a noise, vibration and harshness (NVH) problem for the automotive industry due to warranty-related claims and customer dissatisfaction. Intensive research in the past two decades have provided insight into a number of mechanisms that trigger Brake Squeal. However, Brake Squeal is a transient and nonlinear phenomenon and many determining factors are not known precisely such as material properties, operating conditions (Brake pad pressure and temperature, speed), contact conditions between pad and disc, and friction. As a result, reliable prediction of Brake Squeal propensity is difficult to achieve and extensive noise dynamometer testings are still required to identify problematic frequencies for the development and validation of countermeasures. Here, the influence of uncertainties in friction modelling and contact conditions on friction-induced self-excited vibrations of a 3 x 3 coupled friction oscillators model is examined by combining the linear Complex Eigenvalue Analysis (CEA) method widely used in industry with a stochastic approach that incorporates these uncertainties. It has been found that unstable vibration modes with consistently high occurrence of instability independent of the contact area, friction modelling and sliding speed could be identified. Such unstable modes are considered to be robustly unstable and are most likely to produce Squeal. An example is given to illustrate how instability countermeasures could be designed by repeating the uncertainty analysis for these robustly unstable modes. These results highlight the potential of reliable prediction of Brake Squeal propensity in a full Brake-system using a stochastic approach with the CEA

  • Uncertainty analysis for the prediction of disc Brake Squeal propensity
    2017
    Co-Authors: Zhang Z, Oberst S, Lai Jcs
    Abstract:

    © 2017 Institute of Noise Control Engineering. All rights reserved. ACT Since Brake Squeal was first investigated in the 1930s, it has been a noise, vibration and harshness (NVH) problem plaguing the automotive industry due to warranty-related claims and customer dissatisfaction. Accelerating research efforts in the last decade, represented by almost 70% of the papers published in the open literature, have improved the understanding of the generation mechanisms of Brake Squeal, resulting in better analysis of the problem and better development of countermeasures by combining numerical simulations with noise dynamometer tests. However, it is still a challenge to predict Brake Squeal propensity with any confidence. This is because of modelling difficulties that include the often transient and nonlinear nature of Brake Squeal, and uncertainties in material properties, operating conditions (Brake pad pressure and temperature, speed), contact conditions between pad and disc, and friction. Although the conventional Complex Eigenvalue Analysis (CEA) method, widely used in industry, is a good linear analysis tool for identifying unstable vibration modes to complement noise dynamometer tests, it is not a predictive tool as it may either over-predict or under-predict the number of unstable vibration modes. In addition, there is no correlation between the magnitude of the positive real part of a complex eigenvalue and the likelihood that the unstable vibration mode will Squeal. Transient nonlinear simulations are still computationally too expensive to be implemented in industries for even exploratory predictions. In this paper, a stochastic approach, incorporating uncertainties in the surface roughness of the lining, material properties and the friction coefficient, is applied to predict the Squeal propensity of a full disc Brake system by using CEA on a finite element model updated by experimental modal testing results. Results compared with noise dynamometer Squeal tests illustrate the potential of the stochastic CEA approach over the traditional deterministic CEA approach

  • The Role of Nonlinearity and Uncertainty in Assessing Disc Brake Squeal Propensity
    'SAE International', 2016
    Co-Authors: Oberst S, Zhang Z, Lai Jcs
    Abstract:

    Copyright © 2016 SAE International. Despite significant progress made in the past 20 years in discovering some of the mechanisms of Brake Squeal, it remains difficult to predict the underlying friction-induced instabilities reliably. Most numerical analyses are based on linear deterministic analyses of structural vibrations such as the complex eigenvalue analysis (CEA). However, nonlinear multi-scale processes govern friction contact with high sensitivities to operating and/or environmental conditions. In addition, uncertainties in the material properties and boundary conditions such as contact and friction laws are rarely considered. Hence, it is quite common to underpredict or overpredict the number of instabilities and extensive Brake noise dynamometer tests are still required in industry to ensure acceptable Brake noise performance. In this paper, simplified finite element Brake models are used to illustrate the role of nonlinearity in Brake Squeal. By using nonlinear time series analyses, forced response calculations, dissipated friction work and acoustic radiations, unstable pad modes have been found to be responsible for the instantaneous mode Squeal which, although observed experimentally, cannot be predicted with the traditional linear CEA. By considering coupled spring-mass-damper oscillators representing a pad on a sliding plate, the role of uncertainties of contact stiffness and friction laws in Brake Squeal is examined using probabilities of the positive real part of complex eigenvalues and positive friction work. The implications of nonlinearity and uncertainty for Brake Squeal predictions are discussed. Suggestions on how the new insights gained into nonlinearities and uncertainties can be exploited for practical Brake Squeal analyses in industry are proposed

  • On the potential of uncertainty analysis for prediction of Brake Squeal propensity
    'Elsevier BV', 2016
    Co-Authors: Zhang Z, Oberst S, Lai Jcs
    Abstract:

    © 2016 Elsevier Ltd Brake Squeal is a source of significant warranty-related claims for automotive manufacturers because it is annoying and is often perceived by customers as a safety concern. A Brake Squeal analysis is complex due to changing environmental and operating conditions, high sensitivity to manufacturing and assembly tolerances as well as the not so well understood role of nonlinearities. Although Brake Squeal is essentially a nonlinear problem, the standard analysis tool in industry is the linear complex eigenvalue analysis (CEA) which may under-predict or over-predict the number of unstable vibration modes. A nonlinear instability analysis is more predictive than CEA but is still computationally too expensive to be used routinely in industry for a full Brake finite element model. Also, although the net work analysis of a linearised Brake system has shown potential in predicting the origin of Brake Squeal, it has not been extensively used. In this study, the net work of an analytical viscously damped self-excited 4-dof friction oscillator with cubic contact force nonlinearity is compared with the instability prediction using the CEA and a nonlinear instability analysis. Results show that both the net work analysis and CEA under-predict the instability because of their inability to detect the sub-critical Hopf bifurcation. Then, the uncertainty analysis is applied to examine if it can improve instability prediction of a nonlinear system using linear methods and its limitations. By applying a variance-based global sensitivity analysis to parameters of the oscillator, suitable candidates for an uncertainty analysis are identified. Results of uncertainty analyses by applying polynomial chaos expansions to net work and CEA correlate well with those of the nonlinear analysis, hence demonstrating the potential of an uncertainty analysis in improving the prediction of Brake Squeal propensity using a linear method

  • Influence of contact condition and sliding speed on friction-induced instability
    2016
    Co-Authors: Zhang Z, Oberst S, Lai Jcs
    Abstract:

    Brake Squeal, defined as audible noise above 1 kHz, is triggered by energy provided in the contact area between the pad and the disc and friction-induced instabilities. Owing to customers' demand of reducing vehicle noise and the increasing use of light composite materials in cars, Squealing Brakes remain a major concern to the automotive industry because of warranty-related claims. The prediction of disc Brake Squeal propensity is as challenging as ever. Although friction-induced instabilities are inherently nonlinear and during Squeal the Brake system's operating and environmental conditions keep changing, mostly linear and steady state methods are used for the analysis of Brake Squeal propensity. While many different instability mechanisms have been identified, their interactions and the resulting dynamics are not yet fully understood. Linear instability predictions suffer from over- and under-predictions and have to be complemented by extensive noise dynamometer or in vehicle tests. Recent studies indicate that frictional contact is multi-scaled in nature, highly sensitive and inhomogeneous. Very high local pressures and partial contact separations in the contact interface further complicate its numerical modelling. By studying an analytical model of 3 × 3 friction oscillators using three different friction laws (Amonton-Coulomb, the velocity-dependent and the LuGre friction model) in point contact with a sliding rigid plate and incorporating uncertainties in the contact condition, robustly unstable vibration modes have been identified in our previous research. Here, the number and the combination of friction oscillators engaged in contact are randomised to model imperfect contact. In addition, the effect of the variation in the plate's sliding velocity on the in-stability analysis is investigated with randomised friction coefficient of the Amonton-Coulomb friction model. Results of instability prediction and net work calculations are used to illustrate the sensitivity of the instability to the contact modelling and sliding velocity. The potential of considering uncertainties in contact condition on improving the instability prediction for a full Brake model will be discussed

A. R. Mat Lazim - One of the best experts on this subject based on the ideXlab platform.

  • Experimental studies of friction-induced Brake Squeal: Influence of environmental sand particles in the interface Brake pad-disc
    Tribology International, 2017
    Co-Authors: Mohamed Kchaou, A. R. Mat Lazim, M.k. Abdul Hamid, Abd Rahim Abu Bakar
    Abstract:

    Abstract The disc Brake Squeal is a very annoying sound which affects the customer comfort. The generation of this noise is considered as a structural dynamics and/or tribological problems of the pad-disc system. Unlike drum Brake design, this system is exposed to external environmental sand particles, wear debris and water spray. Their presence into the disc and pad interface may create dynamic and physics phenomena induced by friction surface changes which lead to Brake noise and vibration issues. Thus, this paper aims to investigate the effect of environmental sand particles (silica sand and road sand particles) with a range size of 100–150, 150–200 and 300–400 µm on the Brake Squeal noise occurrences. The sensitivity of the sand particles to produce noise is correlated with the wear scar, friction coefficient and variation of Brake operational parameters. It was concluded that the primary reason for the reduced Squeal noise generation was contributed to the reduced COF with the particle embedment. The analysis of the particle size influence on the Squeal occurrence indicated that a small size of silica sand particle produces less Squeal occurrence than that of road sand particles. However, the biggest silica and sand particles seriously damage the pad surface and reduce consequently the real contact surface, inducing a decrease on the friction coefficient.

  • Squealing characteristics of worn Brake pads due to silica sand embedment into their friction layers
    Wear, 2016
    Co-Authors: A. R. Mat Lazim, M Abdul K Hamid, Mohamed Kchaou, Abd Rahim Abu Bakar
    Abstract:

    Disc Brake Squeal is a very annoying sound and a source of considerable discomfort that leads to customer dissatisfaction. There are various possible mechanisms that could trigger Brake Squeal generation either from a structural dynamics and/or tribological point of view. This research investigates a characterization of worn surface of friction material Squealing with external silica sand particles (SSP). The objective is to study the embedment mechanisms of these particles with different size in the case of a Brake pad/disc system in order to correlate their effect to the friction and dynamic behaviour. In the first stage, the Squealing characteristics, the friction coefficient, and the wear of Brake pads is examined without silica sand. Then, three different sizes of silica sand particles are introduced into the Brake pad/disc interface. Surface topography and friction layers of the Squealing Brake pad with and without the presence of silica sand particle are examined. A correlation between SSP size, Squeal and friction behaviours and embedment mechanism is established to highlight the impact of the introducing particle on the friction layer.

Abd Rahim Abu Bakar - One of the best experts on this subject based on the ideXlab platform.

  • Squealing characteristics of worn Brake pads due to silica sand embedment into their friction layers
    Wear, 2016
    Co-Authors: A. R. Mat Lazim, M Abdul K Hamid, Mohamed Kchaou, Abd Rahim Abu Bakar
    Abstract:

    Disc Brake Squeal is a very annoying sound and a source of considerable discomfort that leads to customer dissatisfaction. There are various possible mechanisms that could trigger Brake Squeal generation either from a structural dynamics and/or tribological point of view. This research investigates a characterization of worn surface of friction material Squealing with external silica sand particles (SSP). The objective is to study the embedment mechanisms of these particles with different size in the case of a Brake pad/disc system in order to correlate their effect to the friction and dynamic behaviour. In the first stage, the Squealing characteristics, the friction coefficient, and the wear of Brake pads is examined without silica sand. Then, three different sizes of silica sand particles are introduced into the Brake pad/disc interface. Surface topography and friction layers of the Squealing Brake pad with and without the presence of silica sand particle are examined. A correlation between SSP size, Squeal and friction behaviours and embedment mechanism is established to highlight the impact of the introducing particle on the friction layer.

  • influence of silica sand particles on disc Brake Squeal noise
    Applied Mechanics and Materials, 2013
    Co-Authors: Ahmad Razimi Mat Lazim, Abd Rahim Abu Bakar, Mohd Kameil Abdul Hamid, Izzat Mohd Asri
    Abstract:

    Researchers in recent years begin to explore on tribological behavior of automotive Brake Squeal phenomena which covers the morphology, chemical composition, friction and wear, phase composition and third body or friction film distribution. However less effort has been made to study the tribological on the influence of small particles on Brake Squeal. During braking condition, both rotor and pads are exposed to road environmental particle which may affect pads surface condition. In order to assess the influence of this particle on Brake Squeal a series of Squeal tests were performed. Silica sand grit particles with a size range between 400 to 200 μm which most available on the road surface were used in this experiment. Brake pad and disc surface characteristics were analyzed before and after Squealing condition using Scanning Electron Microscope (SEM) and Energy dispersive X-ray analysis (EDX). The result shows that the silica sand particles had influence the Squeal and surface behavior of the Brake pad.

  • effects of pad surface topography on disc Brake Squeal
    Applied Mechanics and Materials, 2012
    Co-Authors: Ahmad Razimi Mat Lazim, Mohd Kameil Abdul Hamid, Abd Rahim Abu Bakar
    Abstract:

    Brake Squeal has always been a major NVH problem to many car makers due to significant number of warranty claims. Brake Squeal is a high frequency noise (above 1 kHz) emanating from car disc Brakes that get excited due to one or more mechanisms such as mode coupling, stick-slip, hammering and sprag-slip. This paper attempts to investigate the effects of Brake pad surface topography on Squeal generation. Two pairs of a non-asbestos organic (NAO) Brake pad will be tested on a Brake dynamometer test rig. Surface topography of the Brake pad will be analyzed through microscopic techniques using energy dispersive X-ray analysis (EDX), and optical microscope.

Mohamed Kchaou - One of the best experts on this subject based on the ideXlab platform.

  • Experimental studies of friction-induced Brake Squeal: Influence of environmental sand particles in the interface Brake pad-disc
    Tribology International, 2017
    Co-Authors: Mohamed Kchaou, A. R. Mat Lazim, M.k. Abdul Hamid, Abd Rahim Abu Bakar
    Abstract:

    Abstract The disc Brake Squeal is a very annoying sound which affects the customer comfort. The generation of this noise is considered as a structural dynamics and/or tribological problems of the pad-disc system. Unlike drum Brake design, this system is exposed to external environmental sand particles, wear debris and water spray. Their presence into the disc and pad interface may create dynamic and physics phenomena induced by friction surface changes which lead to Brake noise and vibration issues. Thus, this paper aims to investigate the effect of environmental sand particles (silica sand and road sand particles) with a range size of 100–150, 150–200 and 300–400 µm on the Brake Squeal noise occurrences. The sensitivity of the sand particles to produce noise is correlated with the wear scar, friction coefficient and variation of Brake operational parameters. It was concluded that the primary reason for the reduced Squeal noise generation was contributed to the reduced COF with the particle embedment. The analysis of the particle size influence on the Squeal occurrence indicated that a small size of silica sand particle produces less Squeal occurrence than that of road sand particles. However, the biggest silica and sand particles seriously damage the pad surface and reduce consequently the real contact surface, inducing a decrease on the friction coefficient.

  • Effects of Steel Fibers and Surface Roughness on Squealing Behavior of Friction Materials
    Transactions of the Indian Institute of Metals, 2016
    Co-Authors: Mohamed Kchaou, A. R. Mat Lazim, A. R. Abu Bakar, J. Fajoui, R. Elleuch, F. Jacquemin
    Abstract:

    Noise in vehicle is induced by compounds and surface characteristics particularly in the friction contact. The purpose of the present work is to study the influence of Brake pads containing steel fibers as well as to relate surface roughness on the generation of Brake Squeal. Two Brake pads, steel fiber-free and with steel fiber materials, were studied. It was shown that both the materials generated Squeal noise at frequency between 7 and 10 kHz but with a slight difference in humidity and friction coefficient. This difference was attributed to the tribological aspects of the friction material. It was also found that the pad surface roughness played a significant role towards the generation of Brake Squeal. For the sample without steel fibers, it was evident that the surface was neither covered by compacted third bodies nor contact plateaus were evident. However, for the other sample, the internal structure and the topography showed several cracks.

  • Squealing characteristics of worn Brake pads due to silica sand embedment into their friction layers
    Wear, 2016
    Co-Authors: A. R. Mat Lazim, M Abdul K Hamid, Mohamed Kchaou, Abd Rahim Abu Bakar
    Abstract:

    Disc Brake Squeal is a very annoying sound and a source of considerable discomfort that leads to customer dissatisfaction. There are various possible mechanisms that could trigger Brake Squeal generation either from a structural dynamics and/or tribological point of view. This research investigates a characterization of worn surface of friction material Squealing with external silica sand particles (SSP). The objective is to study the embedment mechanisms of these particles with different size in the case of a Brake pad/disc system in order to correlate their effect to the friction and dynamic behaviour. In the first stage, the Squealing characteristics, the friction coefficient, and the wear of Brake pads is examined without silica sand. Then, three different sizes of silica sand particles are introduced into the Brake pad/disc interface. Surface topography and friction layers of the Squealing Brake pad with and without the presence of silica sand particle are examined. A correlation between SSP size, Squeal and friction behaviours and embedment mechanism is established to highlight the impact of the introducing particle on the friction layer.